For example, the U.S. has less than 5 pct of the world's population but has to consume up to 25 pct of world oil production to maintain a middle class lifestyle. For the world to do the same, we will need more than one earth. And that's already starting given a growing global middle class.

our average is 2.7 global hectares per capita but biocapacity is only around 2.1, which means we are at overshoot even given the current population.

Given a growing global middle class, the ave. footprint will have to increase. Given resource depletion (one good example, as mentioned earlier, is peak oil), increasing population, and environmental damage, the biocapacity will decrease, thus making the overshoot more pronounced.